[vim][feature-request]add cscope support for vim

The official vim port does not have the flag --enable-cscope enabled, which is needed for using cscope within vim properly. I have tried installing cscope then rebuild vim, but it does not work. So that flag is mandatory for using cscope features. In order to use cscope, one have to maintain a modified version of vim port. I think that's a bit inconvenient. So I wish this feature could be enabled in the official port.